MANIFESTATION OF 2-DIMENSIONALITY IN THE CURRENT-VOLTAGE CHARACTERISTICS OF YBA2CU3OX FILMS

Evidence of two-dimensionality in thin superconducting films composed of oriented crystal blocks is found. Extremely large intervals between the mean field superconducting critical temperature and that of the K osterlitz-Thouless transition are obtained. A substantial growth of th e film anisotropy produced by sample heat cycling is found. It is conc luded that at least in the limit of a high current, textured YBa2Cu3Ox films must be regarded not as solid objects but as stacks of two-dime nsional superconducting layers.